10 Fascinating Facts About Your Microbiome

No man is an island, but every man and woman is an ecosystem. That’s the message of the American Museum of Natural History’s new exhibition, The Secret World Inside You, which takes a closer look at the human microbiome. “Microbiome is a term to describe either all the organisms that live in or on us, [and] it’s also sometimes used to talk about genes,” said Susan Perkins, a curator in the Division of Invertebrate Zoology and Sackler Institute for Comparative Genomics, and co-curator of the exhibit along with Rob DeSalle, at a press conference. “We have about 20,000 human genes in our genomes, but hundreds of thousands of microbial genes. We can have between 30 trillion and 400 trillion cells living in us at any given time.”

Visitors to the exhibit will get to know the microbes, both good and bad, that live in our bodies. They’ll see a 6-foot-tall Winogradsky column—a microbial ecosystem created with mud, eggshells, and newspaper scraps—play a game where they try to create a successful and healthy microbiome, and get hands-on with an interactive table that shows the various ways the microbiome affects our health.

“The discovery of the diversity of the microbiome and the implications [for] our health is probably the first time that we’ve had a major medical breakthrough that every one us of could go home and act upon,” Perkins said. “Learning about how we behave, the foods we eat, the things we do, the antibiotics and other medicines that we might take, and their effects on our microbiomes gives each and every one of us the power to do something that directly affects our health, and I find that super exciting. Working on this exhibit these past couple of years has totally changed my outlook. I do not see myself as a lone entity anymore; I am an ecosystem, and I feel very protective of those little guys inside of me.”

The Secret World Inside You opens November 7; here are a few things we learned at the exhibition. For more mental_floss coverage of the microbiome, click here.

1. If you took all the microbes off and out of your body and put them in a bucket, they’d weigh about three pounds—almost as much as your brain.

2. In the womb, babies are protected from microbes—which are harmful to them—by the amniotic sac. They get their first microbial dose as they are pushed out of the birth canal, which is coated with Lactobacillus bacteria (above) and, for a limited time, bacteria from the digestive tract, which travel from the gut shortly before a woman gives birth. The bacteria get on the baby’s skin and in its mouth; when the baby swallows, that helpful bacteria goes right to its digestive system, kickstarting its microbiome.

3. Babies born via Cesarean, meanwhile, get their microbiomes from bacteria on their doctors’ hands and around the room. The long-term effects aren’t known, but being delivered via C-section rather than vaginally could affect immune development and lead to health concerns like allergies and asthma. Some doctors are swabbing newborn babes with bacteria of the birth canal; if the practice is shown to be beneficial, it might become commonplace.

4. If you use antiperspirant, you have 50 times fewer bacteria in your armpits than people who only wash with soap.

5. Brevibacterium livens is a microbe that can be found on your feet, where it eats amino acids and converts them into methanethiol, a super smelly molecule. It’s also used to ripen Limburger cheese. Yummy!

6. More than 1100 different kinds of bacteria can live in the human mouth, including Streptococcus mutans (above), which attaches to the nooks and crannies in your teeth and causes tooth decay. Scientists are working on a vaccine against the microbe.

7. Not many bacteria can survive in the stomach, which is highly acidic. The bulk of microbes—99 percent—live in your digestive tract.

8. Obese people and obese mice have something in common: A deficiency in the gut bacteria Akkermansia muciniphila. Giving obese mice more of the bacteria helped them shed some pounds and restored the protective mucus layer in their intestines.

9. At least one microbe might have more say in how we dress than a fashion blog: Some studies have shown that men infected with Toxoplasma gondii (above)—the same microbe that makes rats and mice unafraid of cats—are sloppy dressers, while women infected with the microbe dress better. T. gondii affects behavior, too: Infected men tend to be rule-breakers, while infected women are more sociable. About one-third of humans are infected with the parasite.

10. Your microbes are all over your house. In one study, scientists found that the bacteria on doorknobs and floors closely matched the microbes on the residents’ skin. The bacterial mix in a house shifted when just one person was gone for a long weekend, and when a family moved, their bacteria populated the new home in just a couple of days.

All images courtesy of AMNH.